Phase transformation.



PATENTED OCT. 4, 1904.

A. D. LUNT. PHASE TRANSFORMATION.

APPLIUATION nun APR. 5, 1902.

NO MODEL.

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UNITED STATES Patented October 4, 1904.

PATENT OFFICE.

ALEXANDER D. LUNT, OF SOHENEGTADY, NEW YORK, ASSIGNOR TO- GENERAL ELECTRIC COMPANY, A CORPORATION OF NEWV YORK.

PHASE TRANSFORMATION.

SPECIFICATION forming part of Letters Patent No. 771,786, dated October 4, 1904:.

Original application filed July 31, 1900, Serial No. 25,418. Divided and this application filed April 5, 1902. Serial No. 101,470. (No model.)

To all whom it may concern:

Be it known that I, ALEXANDER D. LUNT, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Phase Transformation, (division of my prior application, Serial No. 25,418, filed July 31, 1900,) of which the following is a specification.

My present invention relates to a means for transforming three-phase current into twelvephase current or the reverse, and is of particular value for use in connection with rotary converters in which the armature-heating is less the greater the number of phases there are on the alternating-current side of the machine.

In practice I make use of three transformers, each of which is provided with one Winding connected to the three-phase system and three other windings connected to the twelvephase system. In all there are nine windings connected to the twelve-phase system, and these windings are so interrelated that their electromotive forces may be represented by a double delta superposed upon a double Y.

A better understanding of the invention will be had by reference to the following description, taken in connection with the accompanying drawings, while the points of novelty of the invention will be set forth in the claims appended hereto.

Figure 1 is a representation of my invention, and Fig. 2 a diagram of electromotive forces.

The phase transformation is performed, preferably, by a set of transformers having primary windings difiering in number from the secondary windings.

In Fig. 1 three transformers are shown having primary windings A B O, connected, respectively, to three-phase mains, each primary being provided with three secondaries, two of which are identical in current-carrying capacity and'number of turns, while the third has a slightly larger number of turns. Of

course if twelve-phase current is to be converted into three-phase the windings will be reversed in function, those connected to the three-phase mains being their secondaries and the others primaries.

In the present embodiment of the invention all of the secondaries are connected to a rotary converter in such manner as to supply twelve-phase currents thereto. Fig. 1 illustrates this mode of connection in diagram, while Fig. 2 represents the electromotive forces acting in the system and by an arrangement of corresponding lettering is of assistance in explaining the connections in Fig. 1.

For convenience the armature-winding of the converter is represented in Fig. 2 by the circumscribing-circle D, while the points of connection of the winding are indicated by the radial lines, which emanate therefrom at regular intervals, as shown, and which are numbered to correspond with the similarlynumbered taps. connected to the conventional representation of the armature-winding in Fig. 1. The phases of the different electromotive forces acting upon this winding are indicated by the combination of radii and triangles within the circumference of the circle in Fig. 2.

In making up the connections between the transformers and the converter-armature the first step is to connect in delta three of the secondaries of the several transformers, this connection being made in the ordinary manner. In the drawings this delta connection starts at 1 through the transformer-winding to 2 then through a transformer-winding on the next phase from 3 to 4:", then through a transformer-winding of the remaining phase from 5 to 6 and then back to 1 This connects the electromotive forces of the windings in delta, and from points in the connections joining the transformer-windings leads OX- tend to points on the converter-armature separated from each other by one-third of the polar pitch. Referring to the diagram representing the converter-armature, it will be seen that the connections from the secondary terminals 1 2 lead to the taps 1 5, which in Fig. 2 connect to points joined by the chord designated correspondingly as 1" 2". In

like manner the secondary 3 4 is connected to the taps 5 9, spanning the corresponding chord 3 4 while the remaining secondary of the delta is connected across the chord 5 6 thus completing one delta arrangement of electromotive-forces acting upon the converter-armature. The next step is to connect up another delta, but in this case with two of the sides reversed in order to obtain a sixpointed-star arrangement, represented by the two superposed and relatively reversed deltas indicated in Fig. 2. To enable the connections to be readily traced, it may be stated that parallel sides of the two deltas should have the same polarity at their corresponding ends. Thus, for example, the side 1 2 of one delta and the parallel side 1 2 of the other delta should have their similarly-extending ends of the same polarity.

The figures 1 2 as applied to the secondaries in transformer A indicate 'the opposite polarities, while the exponents a b c distinguish between the respective secondaries. A similar lettering is used in connection with the other two transformers. In making all connections between the transformer-secondaries in Fig. 1 a convenient guide may therefore be secured by similarly lettering the diagram of electromotive forces in Fig. 2. Thus the secondary connected to the taps 5 across the chord 1 2 has its terminal 2 at the left-hand end of the winding, as indicated. The similar secondary 1 2 should therefore have its corresponding terminal 2 of the same polarity indicated by the application of the reference character 2 to the left-hand terminal. In a similar manner all the parallel chords are designated by corresponding reference characters, whereby the proper sequence of connections may be readily made by consulting the diagram thus marked. To connect up the second delta,the connections through the various transformers will therefore start at 1 through the winding to 2, then through the winding 5 6, and then through the remaining winding 3 4 back to the terminal 1 ,thus completing a reversed delta. Three connections lead therefrom and are joined to corresponding points of the converter-armature, as indicated by the taps 3 7 11. Thus, to

' illustrate, the tap 7, shown in Fig. 2 as leading to theintersecting ends 2 and 5 of two chords, is connected to their correspondingly-Iettered transformer-terminals in Fig. 1. When it is understood that the apexes of one delta lie midway between the connections of the apexes of the other delta, no diificulty will be found in making the connections to the proper points in the converted armature. twelve-phase connections to the rotary converter, the remaining secondary windings are connected so that each secondary spans a diameter and is symmetrically connected with relation to the other secondaries, whereby the points of connection of one secondary are dis- To complete the placed by an angle of sixty degrees from each of the other secondaries. The points of connection are, however, chosen so as to lie midway between those of the double deltas, thereby constituting therewith a twelve-phase relation of electromotive forces acting upon the armature. In making the connections it is only necessary to remember that the double-Y The coil across the.

ends of the chords parallel to this diameter.

The remaining connections will readily be understood without further explanation.

It will be evident that the currents flowing in the windings of the phase-changing transformers are normally in phase with the electromotive forces generated in the respective windings. The windings therefore are not burdened with wattless currents,and may thus be made smaller than would be necessary in a system of phase transformation in which a flow of wattless current is inherent.

Although for purposes of explanation I have assumed that three-phase current is converted by the apparatus shown into twelvephase current and supplied to a rotary converter, it will of course be obvious that the reverse operation is quite within my invention. In the latter case direct current would be fed into the rotary converter, by which it would be transformed into twelve-phase current and then by the arrangement of transformers shown into three phase current. The exact scope of my invention is, however, to be determined not by means of the above detailed description, but by reference to the following claims.

What I claim as new, and desire to secure by Letters Patent of the Unit-ed States, is-

1. The combination of a dynamo-electric machine havinga winding provided with taps connected thereto in twelve-phase relation, a plurality of sets of transformer-windings, connections interlinking certain of said windings in double-delta relation to each other, and connections between terminals of all of said transformer-windings and said taps.

2. The combination of a plurality of threephase transformer-windings, a twelve-phase dynamo-electric machine, and connections between said machine and said windings such that the electromotive forces of the windings may be represented by a double delta superposed upon a double Y.

3. The combination of threephase mains, transformer windings connected thereto, other transformer-windings inductively related to the first-mentioned windings and connected so as to transfer energy to or from twelve-phase conductors, and an alternatingcurrent dynamo-electric machine connected to said conductors.

4. The combination of magnetic cores constituting seats of three-phase fluxes, windings in inductive relation to said cores and so connected as to constitute seats of resultant twelve-phase electromotive forces, and a dynamo-electric machine connected to said windings.

5. The combination of three sets of transformer-windings, one of the sets connected in delta relation, another in delta relation reversed with respect to the first set, and the third set in double-Y relation, and twelvephase mains extending from the terminals of all of the windings.

6. The combination of windings constituting seats of electromotive forces in double-delta relation to each other, other windings constituting seats of electromotive forces so related as to be represented by a double Y,-and mains extending from the terminals of all of said windings.

7 The combination of multiphase mains, transformer windings connected thereto, other transformer-windings inductively related to the first-mentioned windings and connected so as to carry currents in phase with the electromotive forces of the respective windings, and so as to produce resultant twelvephase current.

8. The combination of multiphase mains, phase-changing windings,twelve-phase mains, and connections between said twelve-phase mains and said phase-changing windings such that the currents flowing in the windings are in phase with the electromotive forces of the windings.

In Witness whereof I have hereunto set my hand this 3d day of April, 1902.

ALEXANDER D. LUNT.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

